Medical status. A standard questionnaire concerning coronary risk factors, medications, and medical diagnosis will be completed at baseline on all subjects. Heart rate and baseline ECG. Resting 12-lead ECG will be recorded using a standard electrocardiograph at the time of the treadmill. Subjects with CVD events evident on their ECG will be excluded. Blood pressure. Resting blood pressure will be measured in triplicate by asculatory techniques using a mercury sphygmomanometer.